1. Field of the Invention
The invention relates generally to distributed generation energy systems and, more specifically, to a distributed generation energy system having an energy management system that optimizes and controls the generation and usage of energy to maintain a desired building environment at minimum cost.
2. Brief Description of Related Technology
Conventional power generation is typically based on a process in which fuel is burned as a source of energy to turn a turbine. For example, in the case of a base load power plant, coal is burned to obtain heat, the heat is converted to steam, and steam pressure is used to turn one or more turbines. The turbines in turn generate electrical power. Unfortunately, conventional power generation is an inherently inefficient process, with much of the total energy value of the fuel source being lost in the form of wasted heat. Typically, only a small fraction of the total energy value of the fuel is extracted from the fuel and ultimately useable as electrical power.
Cogeneration processes have been developed in order to increase the overall efficiency of the power generation process. In contrast to conventional power generation, cogeneration makes use of at least some of the waste heat, usually by extracting a portion of the waste heat from the low-temperature steam exhausted from the turbines. The recovered heat may be used directly in the form of a hot air stream. Alternatively, the recovered heat may be used to create additional steam, which is then used to generate still more electrical power.
Other processes have been developed in the continuing attempts to maximize the overall efficiency of power generation and energy extraction. For example, natural gas is favored as a fuel source because it is clean burning with low emissions. Thus, gas-fired turbines are often used to generate electricity. In some cogeneration power plants, these clean-burning gas-fired turbines are coupled with heat exchangers which extract heat from the stream of hot exhaust gases. The exhaust gases are not released until a maximum amount of thermal energy has been recovered. These gas-fired power plants, which are often manufactured as independent, stand alone units, are therefore more efficient producers of electricity, hot water, or steam, and have the added benefit of producing negligible emissions.
Although cogeneration systems offer increased efficiency relative to more conventional power plants, further increases in overall energy efficiency are desirable.
In accordance with an aspect of the invention, an energy management system is provided for managing the generation and distribution of energy from an energy source to a building. The building has a desired building environment and a total energy profile including a thermal energy requirement and an electrical energy requirement. The energy management system comprises an energy generator arranged to convert energy from the energy source to thermal energy and electrical energy, a heat recovery unit arranged to recover byproduct heat from the energy generator, a cooling unit and/or a dessicant unit arranged to use a first portion of the thermal energy to provide cooling and/or dehumidification, a heating unit arranged to use a second portion of the thermal energy to drive a heating unit, a heat storage unit arranged to store excess heat, and an energy optimizing controller. The energy optimizing controller includes a thermal flow controller and an electrical flow controller, with the thermal flow controller being arranged to distribute the thermal energy and the recovered byproduct heat to at least one of the cooling unit, the heating unit, and the heat storage unit. The electrical flow controller is arranged to distribute electrical energy to at least one of a plurality of electrical components, with the energy optimizing controller being arranged to establish a target total energy cost, calculate an index of performance indicative of an actual energy cost based on an actual electrical load and an actual thermal load, compare the actual energy cost to the target total energy cost, and adjust the distribution of the thermal and electrical energy to thereby obtain a minimum total cost.
In further accordance with a preferred embodiment, a thermally driven dessicant dehumidification system may be employed in order to reduce the humidity within the building, which thus lowers the amount of energy required for cooling purposes. Further, the electrical flow controller may be arranged to distribute electrical energy in the form of alternating current, direct current, or an optimized combination of alternating current and direct current.